It is one of the functions of a PCM channel bank to receive voice frequency (VF) signals from a plurality of VF lines and deliver them encoded and multiplexed in a digital time division multiplexed format. The standard for North America is the 24-channel T1 format.
When encoding each of the VF signals, the encoder encounters a direct current (d-c) offset component resulting from the particular VF signal. Such d-c offset component causes an error above and beyond the normal encoding errors inherent in the encoding process. Methods of counteracting this d-c offset component have included inserting a fixed counter-offset component. However, since the d-c offset component itself varies with time as well as from one VF signal to another, such method of compensation is not fully satisfactory.